SANEAlex, to your question regarding if protons and neutrons can emit a photon:Radioactive decay that produces gamma rays is just that. The protons and neutrons of the atom are in an unstable energy state so it emits gamma photons to reduce its energy state to a more stable one.

Now, before I go on, I had to interpret a lot of your post because I was confused by your grammar, (and I am entirely unsure how the Emperor’s New Clothes come into this). Hopefully I got it right.

To begin. Dark matter (I love this stuff, so much fun and so interesting).Dark matter was proposed to account for the discrepancies between the gravitational effects of galaxies, globular clusters and other large astronomical objects, and the mass of the visible matter. Dark matter can be measured through its gravitational effects on masses and spacetime around it. This is where gravitational lensing comes in, gravitational lensing is a phenomena related to General Relativity, it is observed as light from a source being bent (‘lensed’) around a mass that is between the source and the observer.

Gravitational lensing is one method that we can use to observe dark matter. Dark matter also accounts for the velocities of objects in outer orbits of galaxies. It would be expected without dark matter that the objects would be orbiting slower in order to maintain their orbits, however they do not, they orbit at approximately the same rate. The presence of dark matter accounts for this.

The universe is expanding, the space between stellar objects within galaxies is not expanding. Within a galaxy, the objects will (generally speaking) remain in their orbits due to the gravitational pull of the galactic centre.So your proposal is unnecessary to explain the phenomenon.

Having a the space within a galaxy expand will decrease its density, it will in no way make it ‘look heavier’. Your idea does not provide an alternate explanation for dark matter.

Also, your example:Nope. The moon, if ‘transported magically’ to an outer orbit, but maintaining its current orbital velocity, would shoot off. Its velocity would be too high to maintain a large orbit, and it would spiral outwards.

_________________"Don't tell me that man doesn't belong out there. Man belongs wherever he wants to go--and he'll do plenty well when he gets there."Wernher von Braun, Time magazine, 1958

Firstly thanks for the reply i thought it unlikely i had spotted an easy solution but it would have been fun if i had and a Noble would have been nice but never mind

Rastaban wrote:

Now, before I go on, I had to interpret a lot of your post because I was confused by your grammar, (and I am entirely unsure how the Emperor’s New Clothes come into this). Hopefully I got it right.

Being dyslexic even tho computers have given me the joys of a spell checker my grammar and punctuation can be a bit on the creative side so thanks for bearing with me the Emperor’s New Clothes was my humorous reference to a childrens story as in that i did not think Dark matter was there just like the Emperor’s New Clothes were not.

Rastaban wrote:

The universe is expanding, the space between stellar objects within galaxies is not expanding. Within a galaxy, the objects will (generally speaking) remain in their orbits due to the gravitational pull of the galactic centre.So your proposal is unnecessary to explain the phenomenon.

I did wonder if there was a reason why the space within a galaxy does not expand like the rest of the universe you seem to be saying its because of gravitational pull which is what i was trying to suggest if all space is expanding and the centre of gravity is pulling stuff back together would that not look like a minor modification of the inverse square law? or is there something about conglomerations of matter that stop the expansion locally if so i would have still thought that the further you got out away from the centre of the mass the rate of expansion would change until it reached the value observed in the hard vacuum of the spaces between galaxies what have i missed?

Rastaban wrote:

Having a the space within a galaxy expand will decrease its density, it will in no way make it ‘look heavier’. Your idea does not provide an alternate explanation for dark matter.

What i was suggesting was that it was constantly contracting back down to the more or less the same size and by doing so it made the outer parts move faster than they would be expected to under a vanilla inverse square rule of gravity with no expansion of the universe. And if the outer parts are moving faster than you think they should under the inverse square law then you could be forgiven for thinking that there is Mass that you could not see.

Rastaban wrote:

Also, your example:Nope. The moon, if ‘transported magically’ to an outer orbit, but maintaining its current orbital velocity, would shoot off. Its velocity would be too high to maintain a large orbit, and it would spiral outwards.

Now this may be the place where i went wrong i had thought that a higher orbit would take more energy to maintain my analogy would be a spinning wheel if you marked a point half way between the spoke and the rim and stuck a gram of matter there and a gram of matter on the rim you seem to be saying that that the inner one contains more kinetic energy than the rim one when the wheel moves at x speed which seems counter intuitive to me i would have thought the rim one would have more energy.That why i thought if you moved the moon as i said magically keeping all its energy parameters then i would have thought it would spiral inwards to create a new stable orbit. And i was saying that the "magic" is that the universe is constantly expanding at what seems to be an accelerating rate IIRC especially as the higher orbit would contain more expanded space than the lower orbit.

Anyway thanks again for answering its been interesting thinking about this stuff.

_________________Someone has to tilt at windmills.So that we know what to do when the real giants come!!!!

The angular velocity of an orbit decreases with the height, hence the ISS in LEO (about 300km) orbits the Earth every 90 minutes or so, but a communications satellite in GEO (about 35800 km) goes around once every 24 hours. The linear velocity also decreases with height: the ISS does about (6300+300)*2*pi = 41500 km in those 90 minutes, for 27600 km/h, while the comsat will do (6300+35800)*2*pi = 264500 km in 24h, or 11000 km/h.

Unless you are actively thrusting, there are no spiral orbits. Teleporting the moon outwards without altering its velocity would mean adding to its potential energy, since you're dragging it away from Earth. The moon would be going too fast for a circular orbit at its new altitude, and thus fly farther away. If you move it far enough, it will escape on a hyperbolic trajectory. If you leave it close enough it will move outwards in an elliptical orbit (trading the excess kinetic energy for potential energy in the gravity field) before falling back again (trading back) and ending up with its original speed and at the altitude you teleported it to, but on the other side of Earth, and it would keep going like that.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

The angular velocity of an orbit decreases with the height, hence the ISS in LEO (about 300km) orbits the Earth every 90 minutes or so, but a communications satellite in GEO (about 35800 km) goes around once every 24 hours. The linear velocity also decreases with height: the ISS does about (6300+300)*2*pi = 41500 km in those 90 minutes, for 27600 km/h, while the comsat will do (6300+35800)*2*pi = 264500 km in 24h, or 11000 km/h.

Unless you are actively thrusting, there are no spiral orbits. Teleporting the moon outwards without altering its velocity would mean adding to its potential energy, since you're dragging it away from Earth. The moon would be going too fast for a circular orbit at its new altitude, and thus fly farther away. If you move it far enough, it will escape on a hyperbolic trajectory. If you leave it close enough it will move outwards in an elliptical orbit (trading the excess kinetic energy for potential energy in the gravity field) before falling back again (trading back) and ending up with its original speed and at the altitude you teleported it to, but on the other side of Earth, and it would keep going like that.

I made a mistake in my using the moon teleporting to twice the distance as my analogy as given the figures you and rastaban have given then losing the moon rapidly would be what would happen under my theory if the rate of expansion of the universe were a lot more rapid than it is but the rate of expansion has I think been measured as being quite small so the increase in potential energy would be a lot smaller but I think it still maybe possibly enough to get rid of the need for Dark Matter I will try another way of describing the idea.

If we simplify the Universe to the rubber sheet model often used to show how gravity bends spacetime and look at it from above with an overlay of see thru graph paper that does not stretch or interact with the rubber sheet model jut like dark matter does not interact with ordinary matter

If you then expand every part of the rubber sheet by a small amount but keep all of the other universal constants the same including gravities inverse square law as has been pointed out an object orbiting another object would gain potential energy which it would immediately turn into extra kinetic energy which if it only happened once would change a circular orbit into a more elliptical but if the expansion is constantly happening then I think that as space would be differently expanded from the relative point of view on different points of an elliptical orbit (remember the rubber sheet model) a continuous expansion by constantly changing the direction of acceleration would gradually make elliptical orbits more circular. So a solar system full of lumps of rocks and ice in chaotic orbits would gradually coalesce into planets with more or less circular orbits like ours over a long enough period of time.

The spiral orbit I was describing is what an elliptical orbit would look like against the imaginary graph paper overlaying the rubber sheet model over time. If you had a perfect circular orbit then expansion would make it elliptical but then more expansion would circularise it again.

I hope that was a clearer explanation of the idea as I say my imagination is visual I don't have the maths to prove or disprove it and if someone did the numbers that proved it was wrong I would perfectly willing to accept its wrong I would like to think my idea is testable unlike the Veegtrón that started this thread which seems to to me to be more of a belief system. I saw that given the numbers shown my first example of the moon moving twice its distance it would wizz away but what if the expansion were a lot smaller would it not do as I suggest or do you think orbits would become more elliptical and eventually accelerate away as in a fast expansion version?

The reason I came up with the above idea is because I have some problems with existing ideas of Dark Matter which I will list below maybe some of you have seen explanations that I have missed if so please enlighten me.

If Dark Matter exists then the first thing we know about it is that it has mass and interacts with gravity as we can observe an gravitational effect that was the reason it was hypothesised into existence.

So it has mass and interacts with other things with mass including ordinary matter.

The base unit of dark matter cannot repel itself or it would either be evenly distributed thru the universe cancelling out its gravitational effect or would overlay ordinary matter in exact proportion to ordinary matters gravitational field and if that were the case we would not notice the effect of its additional gravity as its gravity would already be included in what we think ordinary matters gravity is.

So as we observe ordinary matter clumping together in everything from dust sized particles to stellar sized masses due to the effect of gravity its not unreasonable to assume dark matter would also do so.

Gravity seems to be the same thru what we see of the universe so if we had a similar distribution of lumps of Dark matter we would have lumps from dust particle size thru stellar mass size and probably up to including central galactic black hole size.

Now as there does not seem to be a lot of interaction between supposed Dark Matter and ordinary matter we might be forgiven for missing gravity interactions of dust and small rock sized lumps but isn't our tech up to spotting stellar mass lumps

Now I may have missed the astronomy post that gives an explanation but as we are now spotting extra solar planets due to their various jiggling effects on their suns why have we not noticed 90 percent of the suns in our galaxy jiggling because they are binarys or more with stellar mass lumps of Dark Matter

_________________Someone has to tilt at windmills.So that we know what to do when the real giants come!!!!

Rotation of galaxies is only one of the things where dark matter is "needed" to explain the observed behavior. How would your theory explain the gravity lensing effect of massive galaxy clusters, where the visible matter in galaxies in the cluster simply isn't enough to explain the observed effects?

I am suggesting that the expansion of the universe is changing the shape of the already existing gravitational lens over time the larger the volume the bigger the effect as space time and gravity seems to be intimately entwined at least according to Einstein and in most things i am willing to believe him unfortunately i dont have the math to prove it one or the other but my visual imagination can see that if the universe is expanding then shape of a gravity lens would change over time according to your point of view, and to us distance and time are interconnected.

An analogy could be like binoculars with variable zoom if you look at something big the light would be bent at a different angle to if you looked at something smaller with the same field of view.

You are not the only one who has missed to say something: I forgot to mention that the gravitational lensing effect not only is more intense than what visible matter can explain, but also that the distribution of matter in such clusters according to the distortion of background galaxies does not match the distribution of the visible matter.

So that should answer your question about clumping of dark matter: it actually does clump.

Also regarding your "problems" with dark matter: I think it could be wrong to take the term "matter" to literally: it was called that way because the only thing we can measure so far is its gravitational effect and since matter is what carries mass and conveys gravity, "we" called it matter, and since we can't see it, let's name it dark matter.I guess it is more a term to make it easier to talk about the phenomenon and not necessarily a specific concept of what it is. Do we even know for sure that it actually is "matter" at all? Constructed from various particles like ordinary matter is?

SuperShuki,I think that's giving him too much credit.He's just said that mobile phones are waves (lol) and that waves cause coups.

Clearly: mobile phones cause coups.Therefore military coups must be cause by military waves which are caused by military mobile phones.

I could get out a couple of tennis balls and explain physics to him using words with two of less syllables, but he's going to stick to his guns, even if they are prone to miss-firing.

Despite coming from Discworld fandom where feeding trolls is considered humanitarian Victor has managed to make it to my foe list the first time i have done so on any forum(other than spammers) as i like the ideals of freedom of speech and can accept that some people are the flatter bit of the bell curve than me and think if i show tolerance those on the steeper bits may show tolerance to me. But reading the posts its possible to work out Victor has knowing lied rather than just being on a very flat bit of the bell curve so i suspect those links of his maybe to dodgy sites or he just gets pleasure from baiting people either way if the former (i have not clicked and hope others of this forum have not) or if the latter then He may well have gained pleasure at our expense but i have enjoyed discussions with the rest of you so its not a zero sum game . But victor its a shame you have made me a little less tolerant. As some things you have brought up could have made more interesting discussions if done in another way for instance the thought that photons may actually have mass because of the way they exchange momentum with solar sails and the E=MC2 equation etc seems a valid idea to me but its possible that someone on this forum has the knowledge and ability to explain in simple terms how these things can be without photons needing mass.

Rastaban wrote:

SANEAlex,

Refer to Marcus Zotti's post if you have not already.

I did and found the bit on the Pandora cluster very interesting but still have problems with dark matter and will post a reply to Marcus Zotti's post when i manage to get my thoughts into a reasonably rational order

_________________Someone has to tilt at windmills.So that we know what to do when the real giants come!!!!

Both are, as you may see, NASA websites, so I will hold their credibility to a higher standard than wikipedia.

Basically, we know that dark matter is there, I do not think we are certain as to what it is, however.

Perhaps, we should start a new thread about dark matter, if there isn't already one, and use that as a more appropriate place to discuss. It may also lure people with a greater understanding, as I think this thread deters them. (:

_________________"Don't tell me that man doesn't belong out there. Man belongs wherever he wants to go--and he'll do plenty well when he gets there."Wernher von Braun, Time magazine, 1958